The kitchen window in the Diamos house is long and horizontal, stretching out over the sink and counters—just like the sweep of desert outside.

Through the glass in this little-known 1951 house by Nicholas Sakellar, you can see one of the landmarks of Tucson modernist architecture: Up there on the slope to the east, on the other side of Campbell Avenue, stands Judith Chafee's 1975 Ramada house.

It looks just like a dollhouse from this distance, but the combination of modernist and regional elements that made it famous is clearly visible. Above the boxy house is a giant wooden ramada that shelters the home's desert-dwellers from the sun; Chafee borrowed its design from the ocotillo ramadas the Tohono O'odham have used for centuries to make desert life bearable.

Across the street from the Diamos place is another Chafee gem, the 1977 Jacobson residence, known for its beautifully crafted wooden-shelf staircase.

The Diamos house, built on a five-acre Catalina foothills lot west of Campbell for the widow of a Tucson magnate, is a relatively unknown quantity in this distinguished modernist neighborhood. But like both of the Chafee houses, it has made the list of Tucson's best modernist houses—the "Modern 50," compiled by the Modern Architecture Preservation Project of Tucson (MAPP).

Just published this week, the list is meant to educate Tucsonans about the midcentury architectural treasures in their midst, and maybe help preserve them.

"I grew up here. I hated to see these things disappearing," says architect Chris Evans, who serves as vice president of MAPP and helped compile both the new roster of modernist houses and the earlier registry of midcentury modern commercial buildings.

The city has already lost numerous standout modernist buildings, he says, including Chafee's heralded Blackwell House, a small, desert-friendly concrete structure in Tucson Mountain Park, and William Wilde's 1956 College Shop on Park Avenue near the UA. Wilde's Lerner store on Congress Street was brutally rehabbed.

Other significant buildings have been "dipped in stucco," or otherwise modified to conform to contemporary tastes. Nevertheless, Tucson still has a large number of modernist houses, mostly dating from the mid-1940s to the late-1970s.

"The houses are easier to love," Evans says. "The commercial buildings were more severe."

Five of the little-known houses on the Modern 50 list, including the Diamos residence, will be on this Sunday's AIA (American Institute of Architects) Architecture Tour. A highlight of the annual Architecture Week celebrations (the theme this year is "Cool Design for a Hot Climate"), the tour will also send self-guided visitors to four contemporary infill projects and three architects' offices housed in adaptive-reuse spaces.

The Diamos house, now occupied by a retiree who bought it a little more than four years ago, has many of the traits of the modernist style. Rooms flow into one another, and large windows are oriented toward views of the landscape. The living room has unusual curving walls that lead to wall-size windows on two sides, directing a visitor's gaze toward the University of Arizona and Mount Wrightson to the south, and the Santa Catalina Mountains to the north.

Playful geometry abounds. The half-moon living room pulls away from the straight edges of the rest of the house. The front door's archway has been cropped and sliced into a quarter-moon, a shape that's echoed in the asymmetrical fireplace in the living room.

Best of all, a glass spine divides the house's private spaces from the public. A glass hallway connects the private rooms at the west end—the bedrooms and bathrooms—from the public spaces on the east—the living room, dining room and kitchen. The long, narrow glass hallway in the middle of the house opens up to patios on its north and south sides, making the house see-through and, not too incidentally, creating expansive views of Finger Rock to the north.

"The floor plan is remarkable," Evans says, "and the house has large sections of glass and horizontal planes."

Even so, he notes, the house is a bit of a hybrid. The MAPP nominators called it "25 years ahead of its time," for merging regionally appropriate design with modernist principles.

"It's not truly modern," Evans says. "It's one of the first buildings on our list built of burnt adobe. Before that, modern houses were mostly brick. Sakellar was searching for regional expression. The walls are more tied to history" than to modernism.

Architect Sakellar is best known for his designs for Catalina High School and the Wilmot Library, a well-liked structure that almost fell victim to the wrecking ball a few years back. (Sakellar's son Dino is now conducting a renovation sensitive to his late father's vision.)

The house Nicholas Sakellar designed for his own family is also on the tour. Built in 1961, this house near Westward Look also gives a nod to regional design. White plaster on the exterior is meant as an homage to traditional "stucco-over-adobe construction," according to the MAPP registry.

Another burnt-adobe house on the architectural excursion is Tom Gist's family home, which he designed in 1958. In the Craycroft/Broadway neighborhood, the house has "long, low profile and angled walls," Evans says. "You don't see the roof. It has an open plan, living/dining space and a lot of glass." Three screened porches and eight sets of French doors minimize the distinction between indoors and out.

Also included on the tour is the 1959 Finkelstein residence by Ralph Haver, a well-known Phoenix architect. Built around a central courtyard, the house has the classic low, horizontal profile of modernism, along with burnt-adobe bricks. The 1972 Anderson house by David Tyson "uses traditional materials like burnt adobe and oversized rough-sawn lumber in new and innovative ways to enclose a modern floor plan," MAPP's designation declares.

Both houses are in the foothills, and both are nearly in original condition. The same cannot be said of the Diamos house.

About 10 years ago, it suffered from a rehab that was meant to make it charming by 2000 standards. According to the current homeowner, a speculator bought the house with plans to flip it. He came in and replaced patterned concrete tiles with Saltillo tile. He took out the sliding-glass doors whose big panes of glass let in light and big views, and installed French doors with tiny panes.

The worst offense was the addition of a bedroom on the north side of the glass hallway. A piece of the see-through hallway remains, but the new bedroom blocks off much of the light and greatly reduces the view of Finger Rock.

A decade ago, modernism was mostly reviled, though its open-floor plans are now standard in nearly every mass-production subdivision, Evans says. The subdivisions typically sport faux Spanish Colonial tile roofs, though, while high-end custom houses often tend toward modernism. And a growing nostalgia for the style of the America of 50 years ago just may help preserve midcentury design.